In the United States, over 40% of adults have diabetes or pre-diabetes according to recently published NHANES data. The consequences of this burden are well-known. Compared to their non-diabetic counterparts, Americans with diabetes are at much greater risk to die and to develop vascular and infectious complications. The prevalence of type 2 diabetes has increased as a direct result of the exponential rise in the number of overweight and obese individuals in the United States. Although the mechanisms linking obesity with type 2 diabetes are uncertain, increased adiposity is closely tied to insulin resistance, a key physiologic derangement connected to the development of type 2 diabetes. Insulin resistance is also associated with older age and decreased physical activity, well-established antecedents of type 2 diabetes. Despite the strength of the evidence linking these risk factors with insulin resistance and subsequent type 2 diabetes, the underlying mechanism driving insulin resistance is not well understood. Accumulating evidence suggests, however, that decreased capacity to metabolize glucose via oxidative processes (i.e. mitochondrial dysfunction) plays a fundamental role in the development of insulin resistance. For example, a number of small animal and clinical studies have shown that genetic mutations, oxidative stress, abnormal mitochondrial morphology, diminished oxidative gene expression, decreased oxidative phosphorylation, and low aerobic capacity are associated with obesity, insulin resistance, and type 2 diabetes. Despite the emerging consensus regarding the importance of energy homeostasis in metabolic disorders, there are no feasible methods for assessing mitochondrial function in large population-based studies or in clinical populations. Recent evidence suggests, however, that blood and urine levels of molecules involved in glucose metabolism (e.g. lactate, alanine, succinate, and 1- ketoglutarate) are indicators of mitochondrial dysfunction. Therefore, these molecules may be useful tools in the investigation of the relationship between mitochondrial dysfunction and metabolic disorders. Based on this evidence, we hypothesize that mitochondrial dysfunction, assessed by measuring molecules involved in glucose metabolism and energy production is associated with type 2 diabetes and other states of elevated glucose. To test this hypothesis, we propose to measure these factors in the Atherosclerosis Risk in Communities (ARIC) Study, an on-going investigation of atherosclerosis among approximately 15,000 adults from 4 U.S. communities. Our goal is to assess the association of lactate, alanine, succinate, and 1- ketoglutarate with states of elevated glucose and incident type 2 diabetes. If our hypothesis is correct, our study should: 1) confirm the importance of mitochondrial dysfunction in diabetes 2) offer the first set of tools for assessing mitochondrial dysfunction in an epidemiologic or clinical setting, 3) identify risk factors for decreased oxidative capacity and 4) identify genetic variants associated with mitochondrial dysfunction. PUBLIC HEALTH RELEVANCE: The prevalence of type 2 diabetes has increased markedly due to the exponential rise in obesity. Despite its importance, the underlying mechanisms responsible for type 2 diabetes are still poorly understood. In this study, our goal is to examine the role that decreased capacity to metabolize glucose via oxidative processes plays in diabetes in a population-based study consisting of approximately 15,000 people from 4 U.S. communities. If successful, this work could lead to new ways to assess risk for diabetes and its complications in the clinic and to novel approaches for diabetes prevention and treatment.